The present invention relates generally to hybrid electric automotive vehicles, and more specifically, to monitoring the state of charge of the batteries of the hybrid electric vehicle.
Automotive vehicles with internal combustion engines are typically provided with both a starter motor and alternator. In recent years, a combined alternator and starter motor has been proposed. Such systems have a rotor mounted directly to the crankshaft of the engine and a stator sandwiched between the engine block and the bell housing of the transmission. During initial startup of the vehicle, the starter/generator functions as a starter. While functioning as a starter, the starter/generator rotates the crankshaft of the engine while the cylinders are fired.
After the engine is started, the starter/generator is used as a generator to charge the electrical system of the vehicle.
In foreseeable automotive applications, the engine may be shut down during stops (e.g., red lights). When the accelerator is depressed, the starter/generator starts the motor and the engine will resume firing. Thus, many startups may occur over the course of a trip.
Electrical energy from the 42 volt battery of the vehicle is used to turn the starter/generator which in turn is used to start the motor. Consequently, it is important to maintain the battery so that a certain state of charge is provided to allow the battery to provide enough power to the starter/generator to start the engine. Known systems include ammeters to show the charging of the battery but do not provide an indication as to the capacity of the battery to energize a starting component such as the starter/generator. Also, other factors such as the outside temperature of the vehicle are also not considered in such determinations.
It would therefore be desirable to provide a battery charge monitor to provide an indication to the vehicle operator that the battery may not have sufficient charge or capacity to power the starter/generator to start the engine.
The present invention provides a way in which to notify vehicle operators as to the state of the battery. The notification is preferably provided early enough to allow changes to be made so that the vehicle will have enough power to start.
In one aspect of the invention, a method of indicating for a battery of an automotive vehicle comprising monitoring a state of charge of the battery, monitoring a temperature outside of the vehicle, comparing the state of charge to a predetermined state of charge, the predetermined state of charge being a function of the temperature, and generating an indicator when the state of charge reached the predetermined state of charge.
In a further aspect of the invention, a system for an automotive vehicle has a temperature sensor generating a temperature signal indicative of the temperature outside the vehicle and a battery. A battery controller is coupled to the temperature sensor and the battery. The controller monitors a state of charge of the battery and compares the state of charge to a predetermined state of charge. The predetermined state of charge is a function of the temperature. The controller generates an indicator when the state of charge reaches the predetermined state of charge.
One advantage is that the indicator may be provided to the operator in time so that an evasive action may be performed to prevent the state of charge or the battery health to degrade to a point where the battery cannot provide enough power to start the vehicle.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.